A knock-out insert is a device which is inserted into a mold to thereby provide a cavity or opening in the end product. In the concrete industry, it is conventional to provide a concrete housing with a plurality of knock-out openings wherein the concrete is very thin so as to facilitate access to the concrete housing at a plurality of locations.
Knock-out inserts are generally made from sheet metal or wood on a custom basis. I have found that knock-out inserts can be manufactured more economically in the form of modules capable of being coupled together whereby it is possible to meet the demands of most sizes for knock-out inserts. At the same time, the knock-out inserts are capable of being interconnected with one another without the use of bolts or moving parts.